water in vent-pipe above bathroom fan

[foy9999]

bit of a weird one here...

I do slate-roof repairs and have been called to one property many times in recent years for leaks here there and everywhere.

Got an emergency request from them this week as water coming in via the fan in the bathroom

Went today and checked all the slates above the bathroom. It all looked fine.

Next thing was to inspect from inside the attic

Again. all good. No sign of daylight through sarking or water tracking along the woodwork.

I then found that the pipe (to vent on roof) above the fan was wet but only at the bottom. About 8" up from ceiling there was a joint (2 sections of pipe) taped-up with what looked like insulation tape.

The tap was wet and not really holding anything so I removed it and wrapped the joint with Denso tape.

Question is - where would the water be coming from?

There is a hood on the pipe outside and the rubber apron round it is tight and lead flashing was bone-dry under tiles.

The only thing I can come up with is condensation from bathroom was running back down the pipe and out of the taped joint

Seems unlikely but what was it Sherlock Holmes said......

slates, hood, rubber apron and lead flashing all good around vent-pipe

vent-pipe was 2 sections joined with tape and bottom section was wet

pipes now joined with Denso tape but where was water coming from?

 

[brightspark]

its a comon problem hot damp air from the room condensing in the cold pipe and dripping back down in to the fan and on the ceiling you could wrap the pipe with insulation . that would help but it will still condense

 

[angellonewolf]

when i had to fit a fan in the bathroom i was going to fit a tile in the roof but seen meny people moaning about it dripping i vented through the sofit with a solid pipe sloped to the sofit so any condensation goes out that way

 

[brightspark]

if i ever have to fit one and the pipe is already out through the roof i wont guarantee the fan and wont replace it if it gets damaged due to the condensation

 

[gaz1]

wrap insulation around the pipe even that small uplift will cause condensation and it will form more so on the top of the inside cowling then it will drip

 

[brightspark]

it realy should have a condensation water trap fitted with overflow pipe to outside https://www.google.co.uk/search?q=f...gAQGwAQo&sclient=gws-wiz#imgrc=_MGElMJWVQPuAM

 

[500e]

Learn something every day BS, never knew about those fittings, not that it would have helped in our case.
We had a builder at home that used convoluted pipe in a saging horizontal run to the wall outlet, the water pooled in the valleys till it found a small hole then dripped on ceiling

 

[Blue Chips]

its a comon problem hot damp air from the room condensing in the cold pipe and dripping back down in to the fan and on the ceiling you could wrap the pipe with insulation . that would help but it will still condense

it realy should have a condensation water trap fitted with overflow pipe to outside https://www.google.co.uk/search?q=f...gAQGwAQo&sclient=gws-wiz#imgrc=_MGElMJWVQPuAM

When we bought our current house, I found that water had been collecting in the bathroom vent tube and dripping out of the ceiling fan for exactly that reason (condensation). The tube exited the bathroom ceiling fan and passed through the unheated attic to a roof vent. I reinstalled the tube with a LOT of insulation wrapped around the entire length of the tube, all the way up to the roof vent. It apparently solved the problem, because there has been no water at all dripping back through the fan in the nine years we've lived here. My (admittedly amateurish) take on this is that while there may be some initial condensation taking place when I first turn the fan on, I suspect that it might evaporate fairly quickly once the well-insulated inner surface of the tube warms up. That said, I should qualify all of this by adding that we usually let the fan run for several additional minutes after we're done showering and the bathroom is no longer steamy, which might help with evaporation. So far, we've gotten by without a water trap and drainage, but that wouldn't be a bad idea.

 

[123hotchef]

i core drilled my wall to fit my fan with a slight downward slope no messing about condesate drips outwards

 

[123hotchef]

well untill it freezes

 

[brightspark]

i core drilled my wall to fit my fan with a slight downward slope no messing about condesate drips outwards

wall fan arent a problem its its ceiling fans with ducts in to the attic thats a problem, i core through the gable ends for the ducting if possible raise the fan up on a wooden frame and a sloping plank with the duct on top out the wall

 

[angellonewolf]

wall fan arent a problem its its ceiling fans with ducts in to the attic thats a problem, i core through the gable ends for the ducting if possible raise the fan up on a wooden frame and a sloping plank with the duct on top out the wall

yes they are dont ask how i know if you drill the hole with the sloping back to the bathroom you get water coming back in it was meny years ago

 

[brightspark]

got to core 2 fans tomorrow and fit one in wall and one in gable end in attic . wouldnt normaly do them but done loads of work for the punter over the years so wont let them down

 

[Gareth J]

Not turning the heating on this year - normally enough warmer air convects out around the pipe to keep the condensation at bay?

 

[foy9999]

Oh well looks like quite a few votes for condensation

The irony is it's just a W/C, there's no bath or shower and the fan doesn't wor

Well it does but the householder thought it was disconnected.

When I moved the loft-insulation the cable for the fan must've moved and suddenly fan came on.

I told them to get an electrician to check the connection/wiring.

Anyway my point is that with the fan not running and no shower or anything would you still expect much condensation in the pipe?

 

[dobbslc]

That's a good reason I hate domestic work after the lashers have been in!

 

[Blobber]

That's a good reason I hate domestic work after the lashers have been in!

One of the reasons I gave it all up and part P, dont miss rumaging around in insulation and mouse droppings!

 

[dobbslc]

Have you seen this thread?

Bathroom lights- Going from spot lights to single ceiling rose and fan

I would want to be investigating what has caused the charring on the beam, Ceiling needs taking down and then you know what you have got then. Good luck.

www.mig-welding.co.uk

 

[Kram]

We had same problem, fan vent pipe was flat horizontal venting out the wall, or a slight slope , it sagged and collected condensation in the middle. I raised it up several inches so theres now a decent gradient on either side of the fan, condensation can run out the wall or back down the bathroom vent above bath, no issues since.

 

[brightspark]

the best ive seen in a 4 meter flexiduct was about a gallon of water. wasnt funny i pulled it tight and got the lot on my head